Time-hopping sequence for burst mode communications

Abstract

A method consisting of determining, by a symbol mapper, whether a previous burst position is below a threshold, wherein the previous burst position defines a location within a previous symbol. A determination that the previous burst position is below the threshold causes generating, by the symbol mapper, a random number in a complete set, the random number defines a current burst position, the current burst position defines a location within a current symbol and sending or receiving a value in the current burst position. A determination that the previous burst position is above the threshold causes generating, by the symbol mapper, a random number in a reduced set, the random number defines a modified current burst position, the modified current burst position defines a location within the current symbol and sending or receiving a value in the modified current burst position.

1. A method comprising:
 determining, by a symbol mapper, whether a previous burst position is below a threshold, wherein the previous burst position defines a location within a previous symbol; 
 wherein a determination that the previous burst position is below the threshold causes:
 generating, by the symbol mapper, a random number in a complete set, the random number defines a current burst position and the current burst position defines a location within a current symbol; and 
 sending or receiving a value in the current burst position; and 
 
 wherein a determination that the previous burst position is above the threshold causes:
 generating, by the symbol mapper, a random number in a reduced set, the random number defines a modified current burst position and the modified current burst position defines a location within the current symbol; and 
 sending or receiving a value in the modified current burst position. 
 
 
     
     
       2. The method of  claim 1  wherein sending or receiving the value further comprises sending or receiving the value without using a guard interval. 
     
     
       3. The method of  claim 2  wherein sending or receiving the value further comprises sending or receiving the value using pulse-position modulation. 
     
     
       4. The method of  claim 2  wherein sending or receiving the value further comprises sending or receiving the value using on-off keying modulation. 
     
     
       5. The method of  claim 2  wherein sending or receiving the value further comprises sending or receiving the value using phase-shift keying modulation. 
     
     
       6. The method of  claim 1  wherein generating the random number in the reduced set further comprises using a modulus of a sum of a random number in a complete set and a counter as the random number. 
     
     
       7. The method of  claim 1  wherein generating the random number in the reduced set further comprises using a modulus of a symbol index as the random number. 
     
     
       8. The method of  claim 1  wherein generating the random number in the reduced set further comprises using a modulo counter value as the random number. 
     
     
       9. The method of  claim 1  wherein:
 generating the random number in the complete set further comprises generating a random number using a first random number generator; and 
 wherein generating the random number in the reduced set further comprises generating a random number using a second random number generator. 
 
     
     
       10. The method of  claim 1  wherein determining whether the previous burst position is below the threshold further comprises determining that the previous burst position is below the threshold if the location of the previous burst position was in a first half of the previous symbol. 
     
     
       11. The method of  claim 1  wherein the threshold is a function of a channel delay spread. 
     
     
       12. The method of  claim 11  wherein determining whether the previous burst position is below the threshold further comprises determining that the previous burst position is above the threshold if the difference between the previous burst position and the current burst position is less than the channel delay spread. 
     
     
       13. The method of  claim 11  wherein generating the random number in the reduced set further comprises mapping the random number to a set having elements such that the difference between the previous burst position and the modified current burst position is greater than the channel delay spread. 
     
     
       14. The method of  claim 1  wherein at least one of generating the random number in the complete set and generating the random number in the reduced set further comprises using the out put of a linear feedback shift register. 
     
     
       15. The method of  claim 14  wherein at least one of generating the random number in the complete set and generating the random number in the reduced set further comprises using the modulus of the output of the linear feedback shift register. 
     
     
       16. A system comprising:
 a symbol mapper configured to:
 determine whether a previous burst position is below a threshold, wherein the previous burst position defines a location within a previous symbol; 
 wherein if the symbol mapper determines that the previous burst position is below the threshold then, as a result, the symbol mapper:
 generates a random number in a complete set, the random number defines a current burst position and the current burst position defines a location within a current symbol; and 
 sends or receives a value in the current burst position; and 
 
 wherein if the symbol mapper determines that the previous burst position is above the threshold then, as a result, the symbol mapper:
 generates a random number in a reduced set, the random number defines a modified current burst position and the modified current burst position defines a location within the current symbol; and 
 sends or receives a value in the modified current burst position. 
 
 
 
     
     
       17. The system of  claim 16  wherein if the symbol mapper sends or receives the value, then the symbol mapper sends or receives the value and does not use a guard interval. 
     
     
       18. The system of  claim 17  wherein if the symbol mapper sends or receives the value, then the symbol mapper uses pulse-position modulation to send or receive the value. 
     
     
       19. The system of  claim 17  wherein if the symbol mapper sends or receives the value, then the symbol mapper uses on-off keying modulation to send or receive the value. 
     
     
       20. The system of  claim 17  wherein if the symbol mapper sends or receives the value, then the symbol mapper uses phase-shift keying modulation to send or receive the value. 
     
     
       21. The system of  claim 16  wherein if the symbol mapper generates a random number in a complete set, then the symbol mapper uses a modulus of a sum of a random number in a complete set and a counter as the random number. 
     
     
       22. The system of  claim 16  wherein if the symbol mapper generates a random number in a complete set, then the symbol mapper uses a modulus of a symbol index as the random number. 
     
     
       23. The system of  claim 16  wherein if the symbol mapper generates a random number in a complete set, then the symbol mapper uses a modulo counter value as the random number. 
     
     
       24. The system of  claim 16  wherein:
 if the symbol mapper generates the random number in the complete set, then the symbol mapper generates the random number using a first random number generator; and 
 if the symbol mapper generates the random number in the reduced set, then the symbol mapper generates the second random number using a second random number generator. 
 
     
     
       25. The system of  claim 16  wherein the symbol mapper determines that the previous burst position is below the threshold if the location of the previous burst position was in a first half of the previous symbol. 
     
     
       26. The system of  claim 16  wherein the threshold is a function of a channel delay spread. 
     
     
       27. The system of  claim 26  wherein the symbol mapper determines that the previous burst position is above the threshold if the difference between the previous burst position and the current burst position is less than the channel delay spread. 
     
     
       28. The system of  claim 26  wherein the reduced set comprises elements such that the difference between the previous burst position and the modified current burst position is greater than the channel delay spread. 
     
     
       29. The system of  claim 16  wherein at least one of the symbol mapper generates a random number in a complete set and the symbol mapper generates a random number in a reduced set further comprises the symbol mapper uses the out put of a linear feedback shift register. 
     
     
       30. The system of  claim 29  wherein at least one of the symbol mapper generates the random number in a complete set and the symbol mapper generates the random number in a reduced set further comprises the symbol mapper uses the modulus of the output of the linear feedback shift register. 
     
     
       31. A body area network, comprising:
 an impulse-radio ultra-wideband (“IR-UWB”) transmitter configured to apply no guard interval periods per symbol transmitted; and 
 an IR-UWB receiver configured to receive transmissions of the ultra-wideband impulse-radio transmitter; 
 wherein:
 a first symbol is transmitted without a guard interval and using a first burst position; 
 a second symbol is transmitted without a guard interval and using a second burst position; 
 the first symbol immediately precedes the second symbol; and 
 the difference between the first burst position and the second burst position is greater than a channel delay spread. 
 
 
     
     
       32. The body area network of  claim 31  wherein the IR-UWB transmitter is further configured to apply at least one selected from the group consisting of: burst position modulation per symbol transmitted, on/off keying modulation per symbol transmitted and pulse-shift keying modulation per symbol transmitted.